EP0091214B1 - Comparateur de proportions pour signaux digitaux - Google Patents

Comparateur de proportions pour signaux digitaux Download PDF

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Publication number
EP0091214B1
EP0091214B1 EP19830301339 EP83301339A EP0091214B1 EP 0091214 B1 EP0091214 B1 EP 0091214B1 EP 19830301339 EP19830301339 EP 19830301339 EP 83301339 A EP83301339 A EP 83301339A EP 0091214 B1 EP0091214 B1 EP 0091214B1
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EP
European Patent Office
Prior art keywords
bits
groups
indication
prom
order
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Application number
EP19830301339
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German (de)
English (en)
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EP0091214A2 (fr
EP0091214A3 (en
Inventor
Steven S. Chan
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Ampex Systems Corp
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Ampex Corp
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F7/00—Methods or arrangements for processing data by operating upon the order or content of the data handled
    • G06F7/02—Comparing digital values
    • G06F7/026—Magnitude comparison, i.e. determining the relative order of operands based on their numerical value, e.g. window comparator

Definitions

  • the present invention relates to a system for comparing two numbers or words, and more particularly to a system for determining whether the ratio of two binary numbers exceeds a reference value.
  • ROM read-only memory
  • PROM programmable read-only memory
  • the present inyention as claimed provides a method and apparatus for comparing the ratio of two numbers in which the bits of each number are compared in groups comprising less than the total number of bits.
  • the most significant groups of bits for the two numbers are first compared, and if they contain sufficient information to make the comparison, the result thereof is indicated. If the most significant group of bits does not contain sufficient information, the comparison is made based upon the next most significant group of bits that does contain sufficient information.
  • a probable determination of the ratio of the two numbers can be made, based upon the information contained in one group of bits.
  • each of these situations has a unique address in a memory unit dedicated to the next lower order group of bits.
  • this memory unit In response to an input signal indicating that a probable determination subject to verification has been made, this memory unit provides an output signal that indicates the validity of the determination, based upon input information to this memory unit that is not contained in the higher order group of bits.
  • a reliable determination can be made on the basis of more bits of information than those that are actually contained in one group.
  • US-A-3917935 describes a system in which the ratio of two numbers is determined by means of a read-only memory. If both numbers are less than that permitted by the maximum capacity of a system word, input data bits are shifted to more significant values in order to enable a reduction in the capacity of the memory without a commensurate loss of accuracy in the resolution of small magnitudes.
  • US-A-3219982 describes a system in which data is processed serially by groups, beginning with the least signficant.
  • the comparator illustrated in Figure 1 includes a memory section comprised of three memory units that receive two eight-bit input signals indicating the two numbers to be compared. These memory units can be of any suitable conventional type. However, in the preferred embodiment they are programmable read-only memories (PROMs) and are referred to as such hereinafter.
  • the input signals are respectively labelled NUM and DEN to signify their relative positions as the numerator and the denominator in the ratio that is to be compared against a fixed value.
  • the fixed value that is used for explanatory purposes in this description is 0.7. When the ratio is less than or equal to this value, a binary one state is to be indicated, and when it exceeds this value a binary zero state is to be indicated.
  • One of the memory units receives input information relating to the four most significant bits in each of the NUM and DEN signals.
  • Another one of the memory units, a low-order PROM 12 receives the other bits of information, i.e. the four least significant bits, of each of the two input signals.
  • the third memory unit, a mid-order PROM 14, receives the four bits of each input signal having a middle level of significance, i.e. the third, fourth, fifth, and sixth bits of each signal.
  • the high-order PROM 10 provides an output signal that indicates one of three conditions dependent upon the information contained in the input signals. For example, in the situation in which DEN is equal to 240 and NUM is equal to 128, the binary signals provided to the comparator are as shown below: In this case the high-order PROM 10 will be comparing the signal 1000 to the signal 1111, i.e. 8:15. This information is sufficient to determine that the ratio of the two numbers is less than 0.7. Therefore a binary one signal is to be indicated and, for reasons that become apparent hereinafter, the high-order PROM 10 produces an output signal H1 that is the complement of this binary state.
  • the four most significant bits of the NUM and DEN input signals contain sufficient information to determine whether the ratio of the two numbers to be compared exceeds the threshold value. Consequently, there is no need to look at any of the other bits of information in the input signals, and the high-order PROM 10 produces a second output signal H2 that disables the mid-order PROM 14, which in turn disables the low-order PROM 12.
  • the high-order PROM 10 will not be provided with sufficient information to make a determination of the ratio of the two numbers. For example, if NUM is equal to 15 and DEN is equal to 16, the input signals provided to the comparator will be as indicated below: In this case the high-order PROM 10 would attempt to compare a binary one signal with a binary zero signal. This is actually insufficient information to make an accurate determination, and so the high-order PROM 10 should relinquish control over the decision making process and enable the mid-order PROM 14 to make the decision and indicate whether the ratio exceeds the threshold value. The mid-order PROM 14 is therefore enabled by the H2 output signal from the high-order PROM 10 in this situation. The relinquishing of control by the high-order PROM 10 is indicated by an output signal H3.
  • the mid-order PROM 14 is enabled and compares a binary 4 signal to a binary 3 signal. Based upon this information, it provides a binary one output signal M1 to indicate that the detected ratio exceeds 0.7. This indication is provided by the mid-order PROM in the same manner that the H1 output signal is provided by the high-order PROM. Since the mid-order PROM 14 has sufficient information to make a decision, it disables the low-order PROM 12 by means of an output signal M2.
  • the mid-order PROM operates in a similar fashion as the high-order PROM to relinquish control over the decision making process and enable the low-order PROM 12 to provide an output signal L1 related to the detected ratio.
  • the low-order PROM 12 is enabled by means of the signal M2 from the mid-order PROM, which also indicates that it is relinquishing control by means of an output signal M3.
  • the L1 output signal from the low-order PROM 12 is directly applied to one input terminal of a digital switch 16.
  • the M1 and H1 output signals of the mid- and high-order PROMs 14 and 10, respectively, are applied to input terminals of the switch 16 by means of EXCLUSIVE-OR gates 18 and 20.
  • the input terminals of the EXCLUSIVE-OR gates 18 and 20 that do not receive the M1 and H1 input signals are normally biased high, so that they normally invert the M1 and H1 signals. For this reason, the complement of the desired binary output signal STAT is stored in the high- and mid-order PROMs. Conversely, since the L1 signal is not inverted before it is presented to the switch 16, it does not appear as the complement of the desired STAT signal.
  • the switch 16 When the high-order PROM 10 has sufficient information to make a decision, as indicated by a binary zero H3 signal, the switch 16 connects the output terminal of the EXCLUSIVE-OR gate 20 to its output terminal to thereby provide the indication made by the high-order PROM 10 as the STAT output signal. If the high-order PROM 10 does not have sufficient information to render a decision and relinquishes control, the output signal H3 causes the switch 16 to connect its output terminal to the input terminal connected to the EXCLUSIVE-OR gate 18. If the mid-order PROM 14 also relinquishes control over the decision making process, the signals H3 and M3 cause the switch 16 to connect the STAT output terminal to the input terminal that receives the L1 output signal from the low-order PROM 12.
  • the ratio of the numbers being provided to the PROMs for comparison is relatively close to 0.5 or 1.0, for example, the determination that the ratio is less than or greater than the threshold value of 0.7 is highly reliable.
  • the ratio of the two counts is quite close to the threshold value, the reliability of the indication from the PROM decreases. This consideration becomes particularly significant when the counts provided to the PROMs are relatively low.
  • the input signals provided to the high-order PROM will be the same in both cases.
  • the four most significant bits of each number, that are provided to the high-order PROM will be in the ratio 7:10, which lies exactly at the threshold value.
  • the high-order PROM will provide a signal that is a binary zero.
  • this signal will only be correct in the first case, wherein the ratio 112:172 is equal to approximately 0.65.
  • the ratio 124:160 is equal to approximately 0.77, and hence the STAT signal should indicate the binary zero state, i.e. H1 should be a binary one.
  • the information contained in the next one or two bits i.e. the third and fourth bits in these examples, becomes important. Consequently, it is desirable to be able to look at the next two digits in the NUM and DEN input signals to determine their ratio. In other words, it would be helpful to obtain information from the next lower order PROM to aid in a determination of whether the indication of the binary state provided by the high-order PROM 10 is correct or should be modified.
  • each of these pairs of bits comprising the two most significant bits in the input signals to the mid-order PROM are different, they represent a unique addresss signal to the mid-order PROM for each situation.
  • the mapping chart of Figure 4 illustrates those situations, or addresses, in which the H2 output signal of the high-order PROM 10 goes to the binary zero state to enable the mid-order PROM 14. These situations are indicated by the shading in the chart.
  • the shaded block in the upper left-hand corner of the chart corresponds to the situations depicted in Figure 3 wherein the high-order PROM 10 relinquishes control over the decision making process.
  • the remaining shaded portions of Figure 4, labelled A-N correspond to the situations set forth in Table 1. It will be noted that each of these situations lies adjacent the threshold line discussed previously with respect to Figure 2.
  • a four-bit address signal comprised of the two pairs of bits that are common to both the high- and mid-order PROMs provide for sixteen different addresses. However, in the example illustrated in Table 1 and Figure 4, only fourteen such addresses are utilized. If a greater number of addresses are required, the number of bits common to both PROMs can be increased.
  • each of the situations depicted in Table 1 has a unique address location in the mid-order PROM 14. These locations are outlined as blocks in the mapping chart of Figure 5. Referring again to the previous example wherein the ratio of the input signals to the high-order PROM is 7:10, the NUM and DEN input signals to the mid-order PROM 14 are 11XX and 10XX, respectively, where X could be a one or a zero. Thus, the NUM value is in the range of 12-15 and the DEN value is in the range of 8-11. The address of this block is denoted by the reference I in Figure 5.
  • each block comprises sixteen storage locations within the PROM.
  • the particular one of these storage locations that is called upon to provide an output signal indicating the validity of the high-order PROM's indication is determined by the two least significant bits in each of the NUM and DEN signals provided to the mid-order PROM. In other words, these four bits determine the address of one storage location within the addressed block. For example, where the ratio NUM:DEN is 112:172, the address within the block I is 00,11, labelled Y in Figure 5. Since the probable indication from the high-order PROM 10 is correct in this situation, the output signal from this storage location is a binary one. This signal is labelled M4 in Figure 1 and is applied to the other input terminal of the EXCLUSIVE-OR gate 20. This binary one causes the gate 20 to invert the H1 output signal from the high-order PROM 10. However, since the H1 signal is the complement of the desired indication, the appropriate signal is provided to the switch 16 to be transmitted as the STAT output signal.
  • the probable indication from the high-order PROM is incorrect, as noted previously.
  • the address of the storage location within the block I is 11,00, labelled Z in Figure 5.
  • the output signal M4 from this location is a binary zero indicated by the shading in Figure 5.
  • the output signal H1 from the high-order PROM 10 is not inverted by the EXCLUSIVE-OR gate 20. Consequently, the appropriate binary signal is again provided to the switch 16 for transmittal as the STAT signal.
  • the high-order PROM is capable of indcating.
  • the first of these is that the most significant bits in the NUM and DEN signals contain sufficient information to make a decision as to their ratio, and an indication is provided of this ratio relative to the threshold value. In this condition, both the mid- and low-order PROMs are disabled and have no influence upon the decision making process.
  • the high-order PROM does not receive sufficient information to render a decision and therefore relinquishes control over the decision making process and enables the mid-order PROM 14.
  • the high-order PROM has information sufficient to make a probable decision about the binary state of the input signal, but such decision is not totally reliable.
  • the high-order PROM does not relinquish control over the decision making process, but it does enable the mid-order PROM to provide an output signal.
  • This output signal from the mid-order PROM is capable of modifying that of the high-order PROM so that a more reliable signal is provided to the switch 16.
  • the mid-order PROM 14 enables a determination to be made on the basis of the six most significant bits of each input signal without all six bits being compared against one another in unison. In other words, it provides an extension of the capabilities of the high-order PROM by effectively increasing the number of bits upon which a decision is made.
  • the mid-order PROM can either (a) provide a definite indication of the detected ratio and disable the low-order PROM, (b) relinquish control over the decision making process and enable the low-order PROM, or (c) provide a probable indication of the detected ratio and enable the low-order PROM to modify the probable indication, if required.
  • condition (b) occurs, the low-order PROM 12 must provide a definite indication of the detected ratio, by way of output signal L1, since there are no further PROMs upon which it can rely for help.
  • the mid-order PROM 14 which provides a four-bit output signal for each address, i.e. each combination of NUM and DEN signals, can be implemented with a 4x256 bit capacity PROM.
  • the NUM and DEN signals may be desirable to provide an indication whenever either or both of the NUM and DEN signals fall outside a predetermined range of values.
  • the copending application EP-A-91215, filed 12 October 1983 and entitled "Demodulator for Asynchronous Binary Signals" discloses one situation in which it is desirable to do so, in order to switch the frequency of a clock signal.
  • the extra storage capacity in the high-order PROM 10 can be used to provide an output signal H4 whenever the NUM and DEN input signals exceed a predetermined value.
  • the low-order PROM 12 can provide an output signal L3 whenever the input signals NUM and DEN are less than a second predetermined value.
  • the low-order PROM 12 Since the low-order PROM 12 only receives the four least significant bits of each input signal, it is necessary to insure that the indication that the signals are too low is only produced when the bits of greater significance are zero. To accomplish this function, the H3 and M3 output signals are provided to the input terminals of an AND gate 22. This AND gate is enabled only when both of the high- and mid-order PROMs relinquish control over the decision making process, which occurs only when at least the four most significant bits of each of the NUM and DEN signals is zero.
  • the output signal from the AND gate 22 is provided to one input terminal of a second AND gate 24, which also receives the L3 output signal from the low-order PROM 12. This AND gate produces a LOW output signal whenever the PROM 12 provides the L3 output signal and the AND gate 22 is enabled.
  • the comparison of two eight-bit binary signals can be accomplished with a maximum of three PROMs each having 4x256 bit memory capacity, or a total of slightly more than 3000 bits of storage capacity. This is to be contrasted with the more than 65,000 bits of storage capacity that was previously required.
  • the mid-order decision making unit can comprise a number of PROMs, to thereby provide greater overlap between the input signals provided to each of the various PROMs. In such a case, control over the decision making process can be relinquished by an individual PROM in a greater number of situations, as explained previously with regard to the example where NUM equals 15 and DEN equals 16.
  • a slightly larger PROM can be used to provide a greater number of situations in which the decision from a higher order PROM can be modified.
  • a mid-order PROM receiving five bits of each of the NUM and DEN signals would allow an overlap of three bits with the high-order PROM and thereby provide 64 possible modification situations.
  • the decision making capabilities of the high-order PROM can be extended by three bits, i.e. 64 different possible modifications in each situation.
  • the size and number of PROMs, and the bit overlap between PROMs, will depend in each application upon the degree of resolution required vis-a-vis the acceptable memory costs.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Mathematical Analysis (AREA)
  • Pure & Applied Mathematics (AREA)
  • Mathematical Optimization (AREA)
  • General Engineering & Computer Science (AREA)
  • Computational Mathematics (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)
  • Read Only Memory (AREA)
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  • Error Detection And Correction (AREA)

Claims (8)

1. Un procédé pour déterminer par un traitement de signal si le rapport de deux nombres dépasse un seuil, dans lequel les chiffres d'un premier nombre sont comparés par groupes avec des chiffres respectifs d'un groupe correspondant des chiffres de l'autre nombre; les groupes sont comparés dans des unités de mémoire respectives, un groupe à la fois, en commençant par un groupe de plus fort poids, chaque groupe comprenant un ensemble de chiffres en un nombre inférieur au nombre total de chiffres dans le premier nombre précité, et si les groupes de plus fort poids qui sont comparés contiennent une information suffisante pour permettre une détermination concluante, le résultat de cette détermination est indiqué; tandis que si les groupes de plus fort poids qui sont comparés ne contiennent pas une information suffisante pour permettre la détermination concluante, la détermination est effectuée sur la base des groupes de poids immédiatement inférieur qui contiennent effectivement une information suffisante.
2. Un procédé selon la revendication 1, dans lequel la comparaison de groupes de chiffres particuliers peut fournir une indication spécifiant qu'il est probable que le rapport dépasse le seuil, et une comparaison des groupes de poids immédiatement inférieur est effectuée dans le but de vérifier la validité de cette indication.
3. Un procédé selon la revendication 1 ou la revendication 2, dans lequel des groupes de chiffres successifs dans le premier nombre comportent des chiffres communs aux deux groupes.
4. Un système pour déterminer si le rapport de deux nombres binaires dépasse un seuil, comprenant un ensemble d'unités de mémoire (10,14,12), chacune d'elles pouvant fonctionner de façon à comparer les bits d'une paire respective de groupes qui ont un poids similaire dans les deux nombres, et qui contiennent moins de bits que ces nombres, l'unité de mémoire (10) pour les groupes de bits de plus fort poids pouvant fonctionner en premier, et le système étant conçu de façon que si cette unité de mémoire (10) ou, lorsqu'elle est validiée, une unité suivante (14), ne peut pas déterminer de façon concluante si le seuil est dépassé, l'unité (14 ou '12) destiné à comparer les groupes de bits de poids respectifs immédiatement inférieurs est validée pour comparer ces derniers groupes de bits.
5. Un système selon la revendication 4, dans lequel des groupes de bits de poids différents se chevauchent.
6. Un système selon la revendication 4 ou la revendication 5, dans lequel l'unité (10) destinée aux bits de plus fort poids ou l'unité suivante (14) est conçue de façon à fournir seulement une indication parmi trois, à savoir (a) une première indication qui indique de façon concluante si le rapport dépasse le seuil; (b) une seconde indication qui indique qu'il est probable que le rapport dépasse le seuil; et (c) une troisième indication qui signale l'absence de données suffisantes pour déterminer si le rapport dépasse le seuil, l'unité destiné à comparer les groupes de bits de poids respectifs immédiatement inférieurs étant validée sous l'effet de l'apparition de la seconde ou de la troisième indication.
7. Un système selon la revendication 6, dans lequel l'unité destinée à comparer les groupes de bits de poids respectifs immédiatement inférieurs est invalidée sous l'effet de l'apparition de la première indication.
8. Un système selon la revendication 6 ou la revendication 7, dans lequel l'unité destinée à comparer les groupes de bits de poids respectifs immédiatement inférieurs est conçue de façon à modifier la seconde indication conformément à la détermination concluante qu'elle effectue et qui indique si le seuil est dépassé ou non.
EP19830301339 1982-04-02 1983-03-10 Comparateur de proportions pour signaux digitaux Expired EP0091214B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US36492382A 1982-04-02 1982-04-02
US364923 1982-04-02

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EP0091214A2 EP0091214A2 (fr) 1983-10-12
EP0091214A3 EP0091214A3 (en) 1985-04-17
EP0091214B1 true EP0091214B1 (fr) 1988-06-15

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EP (1) EP0091214B1 (fr)
JP (1) JPS58184650A (fr)
DE (1) DE3377086D1 (fr)
NO (1) NO165169C (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1262866A1 (fr) * 2001-06-01 2002-12-04 STMicroelectronics Limited Procédé et circuit pour déterminer la validité de l'information
FR2965946B1 (fr) * 2010-10-07 2012-12-14 Commissariat Energie Atomique Systeme d'ordonnancement de l'execution de taches cadence par un temps logique vectoriel

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3219982A (en) * 1961-11-14 1965-11-23 Ibm High order mark system
FR2140321B1 (fr) * 1971-06-10 1974-03-22 Dassault Electronique
US3917935A (en) * 1974-12-23 1975-11-04 United Technologies Corp Reduction of look-up table capacity
US4313174A (en) * 1980-03-17 1982-01-26 Rockwell International Corporation ROM-Based parallel digital arithmetic device

Also Published As

Publication number Publication date
EP0091214A2 (fr) 1983-10-12
EP0091214A3 (en) 1985-04-17
NO165169C (no) 1991-01-09
JPH0142007B2 (fr) 1989-09-08
JPS58184650A (ja) 1983-10-28
NO831142L (no) 1983-10-03
DE3377086D1 (en) 1988-07-21
NO165169B (no) 1990-09-24

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